It is a century or a centennial
A period of 100 years is called a century.
The year 1013 AD.
It COULD be called a Gigayear, but in practice it is simply called "a billion years".
An anniversaryanniversary: the annual celebration of an event on that day of a previous year
An 150 year celebration is called a Sesquicentennial celebration
A 175-year celebration is commonly referred to as a "quasquicentennial" or a "septaquintaquinquecentennial." The term "quasquicentennial" is derived from the Latin words "quasqui" meaning "one and a half" and "centennial" meaning "a hundred years." Alternatively, "septaquintaquinquecentennial" combines the Latin words "sept" for "seven," "quinta" for "five," and "quinquecentennial" for "500 years," emphasizing the milestone of 175 years.
An 150 year celebration is called a Sesquicentennial celebration
It is called a "centennial celebration"
A 100 year celebration is called a centennial celebration.
60 year celebration
55th wedding celebration is Emerald.
Centennial
It is called Centenary.
Diamond Jubilee
It is a century or a centennial
An Emerald anniversary